Why does the Code3/Spearco unit report a .7 pressure drop @ around 14PSI
But the Spearco unit reports a .2 pressure drop @ around 14 PSI

The 0.2 pressure drop is probably across only the core and, to be honest, that sounds a little far-fetched to me (Helix advertises a 0.5 psi drop at the core alone at 600CFM and that seems reasonable).

Part of the problem with comparing pressure drops will be to make sure they're at the same CFM (or at least the same psi). And if the figure doesn't include the end tanks, its basically worthless (as far as comparing it to other brands).

Likewise, the temperature reduction % is also kind of sketchy. AA has the "worst" data, but that's probably because they tested in 100+ temps at 30+% humidity. And like was mentioned in the first post of the thread, a heavy IC will act like a heat sink so it'll do better for short bursts with poor airflow (like on the dyno).

Ideally, you'd have some generous benefactor pay $10K+ to buy and test all of the ICs under the same conditions. But since that isn't likely to happen, just documenting what you can will have to do...

So question: Just how much does frontal area matter, how big of an effect does it have when compared to volume?

That's actually a tough question because there is a lot of stuff acting behind the scenes. To (over)simplify, here are some very general rules on ICs:

Longer Intercoolers:
Cool better*
Have more pressure drop

Taller ICs:
Cool better*
Have less pressure drop

Thicker ICs:
Cool slightly better
Have less pressure drop

*Assuming that all of the IC face is still exposed to fresh air

So I'm not even sure if "Volume" is that useful of a reference. To go into a little more detail (on Cores alone), here is some data from Bell:

IC #1:
3x12x12
Frontal area: 144
Volume: 432
CFM: 619

IC #2:
3x6x24
Frontal area: 144
Volume: 432
CFM: 237

IC #3:
3x24x6
Frontal area: 144
Volume: 432
CFM: 1385

I've simplified it so all 3 intercoolers have the same frontal area and volume , but you can see that the taller/shorter the IC, the better it flows.

Not lets take IC #2 and play with lengths:

IC #2:
3x6x24
Frontal area: 144
Volume: 432
CFM: 237

IC #4:
3x6x12
Frontal area: 72
Volume: 216
CFM: 302

IC #5:
3x6x6
Frontal area: 36
Volume: 108
CFM: 350

This should make sense -- the longer the intercooler, the more restriction -- which means the lower the CFM at a given pressure drop. IC #2 will cool best out of this group, IC 5 will flow best...

Now lets take IC #1 and play with thickness:

IC #1:
3x12x12
Frontal area: 144
Volume: 432
CFM: 619

IC #6:
4.5x12x12
Frontal area: 144
Volume: 648
CFM: 928

IC #7:
6x12x12
Frontal area: 144
Volume: 864
CFM: 1238

IC #7 won't cool twice as much as IC #1, but it will still cool a little better. And it flows twice as much.

OK, so the above should make flow rates fairly clear -- but it's still lacking some details on heat transfer:

Newton's Law of Cooling:

Q = Thermal energy in joules
h = Heat transfer coefficient
A = Surface area of the heat being transferred
T = Temperature of the object's surface and interior (since these are the same in this approximation)
Tenv = Temperature of the environment
ΔT(t) = T(t) − Tenv is the time-dependent thermal gradient between environment and object

Before your eyes glass over, it isn't that bad. For our Air-to-Air ICs, all we need to see is:

The more surface area -- the more heat transferred
The greater the temperature difference -- the more heat transferred

Pretty simple, right? So let's see how it applies to the various core dimensions:

Longer Intercoolers:
* Increase total surface area (more heat transferred)
* Increases the time the charge air spends inside the intercooler (more time for heat to transfer, but less efficiently at the end of the IC than beginning. Remember that the greater the temperature difference, the more heat transfer, and the charge air will cool as it passes through the IC so deltaT is lower near the outlet).

Taller Intercoolers:
* Increase total surface area (more heat transferred)
* No change in time the charge air spends inside (IC efficiency doesn't drop off as much from one side of core to other)

Thicker intercoolers:
* Increase total surface area (remember there are comparably more fins even though frontal area is unchanged). However, the ambient air temperature goes up as it passes through the IC (ambient at entrance of IC, hotter in middle, hottest at exit). So while the total surface area increases, the heat exchanging efficiency decreases the thicker you go since the temperature gradient becomes smaller.

From this we see that the most efficient IC for maximum heat exchange and minimal pressure drop is going to be a short, tall IC (pretty much the opposite of the stock IC). The compromises start when we need to worry about airflow -- does the bumper block airflow to the top of the IC? Will the IC block airflow to the radiator (or heat it up too much)? Ah, now the factory design starts to make more sense...

OK, so why not just go with the biggest sucker that will fit? Larger cores cost more, but more importantly, they also increase lag. Ideally you match the core to your power & cooling needs (someone running race gas on the road course in Canada will want a smaller IC than someone trying to get the same power from pump gas in Texas for highway racing).

Still with me? "But wait, there's more..." All of this assumes that each shop is using comparable cores & end tank designs (they're not!).

I was set on buying the HPF intercooler, but it seems to be too big for my needs and also too thick which is not ideal, from what I read...hmm...tough choice

I bought a Stett a few months back that I haven't installed. According to the info on this thread and what I've read since, the actual bar and plate of the Stett is great. The "problem" is the end tanks because their are boxy.. anyone ever tried to replace the end tanks of an IC before??

Note that the temp reduction % is flawed in that I didn't record the boost level & ambient temps. At/near stock boost and in low temps, the stock IC won't do poorly so ICs tested at higher boosts might appear to do better.

Note that the temp reduction % is flawed in that I didn't record the boost level & ambient temps. At/near stock boost and in low temps, the stock IC won't do poorly so ICs tested at higher boosts might appear to do better.

Not that I don't appreciate it, but the temperature reduction is not even remotely accurate. I tested long gear pulls on the AA and had an average reduction of 38F and you are saying 16%??? Second, percentage drop is not a good measure at all of intercooler efficiency. You should be logging absolute temperature drop or temperature above ambient. You should also refuse to use data that is not standardized, i.e. long gear pulls.

Not that I don't appreciate it, but the temperature reduction is not even remotely accurate. I tested long gear pulls on the AA and had an average reduction of 38F and you are saying 16%??? Second, percentage drop is not a good measure at all of intercooler efficiency. You should be logging absolute temperature drop or temperature above ambient. You should also refuse to use data that is not standardized, i.e. long gear pulls.

A standardized test would be great -- what do you propose? (boost level, gear/speed, ambient temps, time)

This is by far one of the most useful posts I have read in awhile. Really appreicate the effort you guys have put towards helping us beginners select the right products. Really have to hand it to spdu4ea for his informative posts. I'm in the market sometime in the near future for a FMIC, and this post has been bookmarked. I really wish I had the time some of you guys have to do all these reviews and test products.

A standardized test would be great -- what do you propose? (boost level, gear/speed, ambient temps, time)

the best comparisons we can all make is if people(end users not tuner data) do a 2-3-4 gear wide open throttle run datalogging boost,rpm and ambient temps. i have a very good calculator that can estimate pre intercooler temps and translate that into intercooler efficiencies using the estimated pre intercooler temps/post intercooler temps and ambient temps. the standardization done this way over multiple gears also shows an intercoolers ability to thwart heat soak... most of the current 2-3-4 data is done at 13.5-14.5psi boost levels, as you said earlier comparing data at stock boost to tuned boost is useless and can be wrongly interpreted. I just want the TRUTH to be shown, as many people it seems get caught up in a name or believe marketing hype... Let independant DATA and FACTS be the judge!

I have proposed an intercooler shootout on several threads, Helix will gladly put our FMIC in the mix as I know from the data i have seen on the opposition we will be at or very near the top of the heap in every apspect: pressure drops, ait drops, intercooler efficiency and reluctance to heat soak

Last edited by TurboBullett@Ambient Thermal Management; 02-03-2010 at 01:49 PM.